Metering device for withdrawing and dispensing a melt and method for producing the metering device

ABSTRACT

A metering device ( 10 ) for withdrawing and dispensing a melt consisting of or containing an oxide fibre reinforced oxide ceramic composite material.

The invention relates to a metering device, preferably to a meteringcrucible or container for vacuum-assisted metering, for withdrawing anddispensing a melt, preferably a metal melt, in particular a non-ferrousmetal melt, in particular an aluminum melt or a melt containingaluminum.

The invention relates in particular to the field of processing of metalmelts, in particular non-ferrous metal melts, preferably aluminum melts,the melt being drawn in by negative pressure and then poured for exampleinto a mold. A spout of a so-called metering crucible is here usuallyimmersed into a liquid aluminum melt, where if necessary an oxidecoating must be broken through.

Corresponding metering crucibles can be produced from a monolithicceramic such as aluminum titanate. Typical wall thicknesses are between10 and 25 mm.

After immersion into the melt, the latter is drawn into the meteringcrucible by negative pressure. The pressures are usually <800 mbar.After the required filling of the crucible, it is closed on the intakeopening side by means of a stopper consisting for example of siliconcarbide. With an automatable movement device, preferably a robot arm,the crucible is then pulled out of the melt and aligned on a mold.

The melt flows out as the stopper frees the opening and at the same timenegative pressure is reduced to a certain extent.

The wall thickness and the high density of aluminum titanate (3.7 g/cm³)result in the disadvantage that the thermal shock resistance of thematerial is negatively affected. The heating up of the crucible for highcomponent volumes takes a long time. There is a risk of solidificationof the melt due to heat dissipation.

The drawback of the known metering crucibles is also that only moderatemechanical characteristic values are attained with bending strengths ofconsiderably less than 80 MPa, and a brittle fracture behavior and thealready mentioned low thermal shock resistance can be observed. Due tothe immersion of the crucible, a large thermal gradient results alongthe axis and along the wall thickness. The required thermal shockresistance is not met due to the unfavorably low thermal conductivity ofaluminum titanate (second thermal shock parameter).

It can also be observed that the crucible material reacts withaggressive aluminum melts which are processed for example duringfinishing or grain refining or other alloy compositions, in particularalkaline melts containing sodium or strontium additives. The resultantreactions lead to a successive destruction of the metering device, andin the case of severe corrosive/chemical attack also to a contaminationof the melt.

It has also been shown that the aluminum titanate has an unfavorablewetting behavior, so that buildups of solidified aluminum until thestopper seizes up in the metering crucible can be observed. In thiscase, dismantling must be performed in the cold state, with the resultthat abrasions caused thereby can lead to wear and destruction of themetering crucible and stopper.

The monolithic ceramic of aluminum titanate is porous and covered withfissures in order to improve the thermal shock behavior. The cruciblesare produced by slip casting of particle-laden slurries. The slipcasting method has disadvantages with respect to component geometry orwall thicknesses. In the slip casting method, the wall thickness insidethe component cannot in general be varied. The maximum wall thickness islimited. The wall thickness is proportional to the root of the castingduration. During the casting process, the formation of gradients canoccur due to differing particles. Disadvantages are also evident duringsintering of high-volume components. Also, the shrinkage occurring leadsto considerable problems in high-volume components.

The object underlying the present invention is to improve a meteringdevice of the type mentioned at the outset such that a reproducible,rapid and precise metering of metal melts, in particular aluminum melts,is possible without the formation of melt artefacts, contamination ofthe melt or air pockets, where the metering device should be usable fora vacuum-assisted casting process and the metering device should bemovable.

To solve the problem, the invention substantially provides that themetering device consists of or contains an oxide-fiber-reinforced oxideceramic composite material with an open porosity in particular of 20% to40%.

If appropriate, the metering device consisting of theoxide-fiber-reinforced oxide ceramic composite material can be coated onthe surface side or compacted. Surface side means inside or outside orboth inside and outside.

To do so, it is in particular provided that the oxide-fiber-reinforcedoxide ceramic composite material is coated at least in some areas, inparticular on the outside, to form a preferably closed-pore coating. Itis possible here for glass solder or organometallic compounds to be usedas coating material.

In particular, the invention provides that a ceramic coating, aprecursor-based coating or a glass-like coating is applied to the basicbody.

There is the possibility for the coating to be applied by thermalspraying.

The composite material contains oxide ceramic fibers, formed frompreferably at least one material from the group Al₂O₃, SiO₂, ZrO₂, Y₂O₃,TiO₂, CaO, MgO, Y₂O₃-stabilized ZrO₂.

It is furthermore provided that the composite material contains an oxideceramic matrix, formed from preferably at least one material from thegroup Al₂O₃, SiO₂, ZrO₂, Y₂O₃, TiO₂, CaO, MgO, Y₂O₃-stabilized ZrO₂.

It is in particular provided here that the matrix and the fibers consistof or contain the same oxide ceramic material(s), or the mainconstituents of the matrix and the fibers match, e.g. consist of Al₂O₃.

It must be particularly emphasized that the metal in the compositematerial and that of the melt or main constituent of the melt should beidentical.

Due to the use of the oxide ceramic composite material, a non-brittlematerial is provided which exhibits thermal shock resistance, sufficientmechanical strength and, regardless of the porosity and surprisingly,the required vacuum tightness. There are no solidification processes orthe formation of inhomogeneities. This increases process reliabilitywhen processing the melt.

Furthermore, advantageous wetting and corrosion properties have beenrevealed in particular during the metering of aluminum melt when themetal of the oxide ceramic composite material is aluminum, i.e. thefibers and the matrix too consist of or substantially contain Al₂O₃. Agood resistance to alkaline aluminum melts is also evident, so that anexpansion in the range of applications can be achieved.

Due to the identical metals, contaminations of the melt by the materialof the metering device or crucible or container are ruled out.

Use of the oxide ceramic composite material enables a low componentweight to be achieved in comparison with the prior art, so that theprocess can be accelerated during metering. Wear on the automatablemovement device or robotic unit is also lower in comparison with theprior art, since lower masses have to be moved.

The metering device itself can be produced by winding fibers onto a diereplicating the internal geometry of the metering device or by the useof textile fabrics, meshes and mats from the oxide ceramic fibers. Theresult of this is advantages in particular regarding the geometricaldesign of the metering device, allowing design improvements to beachieved.

The internal geometry is identical to the interior of the meteringdevice into which the melt is drawn by suction.

Ventilation possibilities and the attachment or integration of heatingelements are possible due to the low wall thickness. The low wallthickness furthermore offers the advantage that only a small amount ofheat is withdrawn from the melt, so that work is possible at a meltingtemperature which is lower in comparison to the prior art. This resultsin energy advantages. Structures necessary for handling of the meteringdevice can be formed without any problem. Thanks to the low weight,simple assembly is possible. Regardless of that, simple production ispossible.

DE 10 2013 104 416 A1 relates to monolithic ceramics with fabric meshreinforcement that are used for construction and for armor plates. Theceramic can also be used for graphite reinforcement.

The subject matter of WO 2016/184776 A1 is a composite tube consistingof two coatings, one of which consists of a non-porous monolithic oxideceramic and one of an oxide fiber composite ceramic.

A method for producing a component of fiber-reinforced compositematerial is shown in DE 10 2010 055 221 A1.

Oxide ceramic composite materials having oxide ceramic fiberreinforcements are known. To that extent, reference must be made forexample to EP 2 848 509 A1 or to DE 10 2016 007 652 A1.

Turbine vanes and turbine blades of steam turbines are described as anexample of application for a corresponding material in DE 10 2017 202221 A1.

A use for areas in which vacuum-assisted operation is required—as incasting processes—does not however exist, in particular against thebackground that it should be assumed due to the porosity thatcorresponding materials are unsuitable for vacuum processes.Surprisingly, it has however become clear that a reproducible, fast andprecise metering of non-ferrous metal melts is also possible when oxideceramic fiber-reinforced composite material in accordance with theinvention is used.

Thin-walled metering containers or crucibles, where necessary withsupplementary components or attached elements, can be produced from theporous oxide-fiber-reinforced oxide ceramic, the volumes being designedsuch that up to 50 kg of melt can be received and transported withoutany problems.

The individual fiber filaments, which are in particular combined asfiber bundles or rovings with several hundred individual filaments,should have a diameter between 5 μm and 20 μm, in particular between 10μm and 12 μm. The density should preferably be between 2.0 g/cm³ and 6.0g/cm³, more preferably between 3.0 g/cm³ and 4.0 g/cm³.

If the open porosity, i.e. the cavities in the metering device or itsoxide ceramic composite material which are linked to one another and tothe environment, can be in the range between 20% and 40%, then the rangebetween 27% and 32% must be specified for preference. Due to the openporosity, a low conductivity of the melting device of in particular lessthan 10 W/mK is achieved.

The wall thickness of the metering device, i.e. of the crucible orcontainer, should be preferably between 1 mm and 20 mm, more preferablybetween 1 mm and 4 mm.

The geometric design is variable and can in particular berotation-symmetrical.

The invention also includes the metering device being designed as aninsert for a metallic structure. This renders the metallic structure ofthe melt, which could otherwise be destroyed, non-attackable.

In particular, it is provided that further components connected to themetering device are produced from the same oxide ceramic material as themetering device.

As already mentioned, the metering device can be produced by a windingtechnique or on the basis of semi-finished textile fiber products, suchas fabrics, meshes and mats.

As already mentioned, the invention does not rule out that a coating isadditionally provided.

Single-layer or multi-layer coatings or coating systems, preferably withthicknesses in the range between 50 μm and 2 mm, can be used as coatingsto reduce gas permeability. The structure of the basic body, i.e. theoxide ceramic composite material, should be largely retained here.

The composite material is generally speaking infiltrated or modified bythe coating only superficially up to a depth of 500 μm, to permit a goodcoating adhesion.

To reduce the gas permeability, the porosity of the coating(s) should beconsiderably less than that of the basic material.

In particular, it is provided that the coating(s) is/are closed-pore,preferably achieving a density of at least 97% of the theoreticaldensity of the coating material. Theoretical density is understood to bethe density at which a body produced from the material has no pores.

The gas tightness should be improved by the coating, such that themetering device can be coated on the inside, i.e. on the melt side, oron the outside. A coating both inside and outside is of course also notruled out.

The coating material can preferably be identical to that of the basicbody, i.e. of the oxide ceramic material.

The coating material can consist of crystalline and of oxide ceramicconstituents.

Regardless of this, the coating material should be temperature-resistantup to 1200° C. and resistant to corrosion and to abrasion.

The metering device can be coated on one side or on both sides, i.e.inside and outside. A coating can also be limited to defined areas.

Possible coating variants are for example the application of glasssolders, precursor-based coatings or thermal spraying.

With so-called glass solders, a glass-like coating crystallizes on thesubstrate by a temperature treatment in the course of production of thecoating. The coating particles are applied by a slurry, e.g. usingbrushes. To that extent, reference is made to the disclosure of DE 102014 106 560 B3 or EP 2 942 342 A1. With a corresponding applicationmethod by means of glass solder, a dense ceramic coating is formed.

In the case of the precursor-based coatings, liquid organometalliccompounds can be used. Application is wet-chemical, for example byspraying or immersion. These compounds pyrolyze, ceramicize andcrystallize fully due to temperature treatment. The volume shrinkage inthe course of processing can be reduced by adding passive and activefillers.

Passive fillers can be for example aluminum oxide or zirconium oxide.Active components in the coating would be Al, ZrSi₂, TiB₂. The latteroxidize in the course of the synthesis and a volume increase results.

With thermal spraying, the coating particles are melted on with the aidof a torch, for example plasma jet or arc, and applied to the substrateby a gas stream. The melted-on particles impact the substrate, flattenand solidify. On impact there is a mechanical interlocking of thesubstrate and particles. A further temperature treatment is notnecessary.

The coating material used for thermal spraying should, for reasons ofthermomechanical and thermodynamic compatibility, be one matching thesubstrate material, i.e. the composite material, in respect of the mainconstituents. If a composite material of Al₂O₃ and ZrO₂ is used, thenthe particles should also consist of Al₂O₃ and ZrO₂. Thermal sprayingworks with appropriate particles consisting of these materials. However,it is also possible to work reactively with aluminum, which oxidizeswhen the substrate material has Al₂O₃ and ZrO₂ as its main constituents.From the expansion for Al₂O₃, YAG (yttrium aluminum garnet) andY₂Si₂O₇/YSiO₅ are suitable.

A coating system can be applied that forms one coating overall. Coatingsystems are several individually differentiable layers of a coating. Forexample a coating system can consist of a bond coat for bonding, a TBC(thermal barrier coating) for thermal insulation and on the outside,i.e. on top, an EBC (environmental barrier coating) as a corrosionpreventer. Each individual layer has a specific function. An expansionmismatch can also be reduced by coatings with graduated buildup.

Depending on the coating method, the penetration depth can be varied.The term penetration depth is intended to express that there can be atransitional area between coating and substrate. If organometallicprecursors are used, they penetrate deeper into the substrate materialand infiltrate it, resulting in some cases in a reaction between coatingmaterial and substrate.

In thermal spraying, the melted or partly melted particles impact thecolder substrate surface, resulting in a mechanical adhesion. In thiscase, the penetration depth is very low, or only a superficial adhesioncan result, so that in practice it cannot be regarded as a penetrationdepth.

Regardless of how the coating is produced, the properties of thesubstrate material are retained. The coating results in the advantagethat embrittlement does not occur. An increase in the gas tightness isachieved due to the coating. The coating has a high degree of hardnessand offers both abrasion and corrosion resistance.

In particular, the teachings in accordance with the invention arecharacterized in that fiber reinforcements designed to cope with theload can be provided. Thicker material can thus be provided, inparticular in the dispensing and hence the withdrawing area of themetering device, to protect areas of increased load.

The geometrical restrictions occurring according to the prior art whenusing monolithic ceramics do not apply.

In particular, it is provided that a corresponding metering device isdefined to process non-ferrous metal melts that consist of or containAl, Si, Mg, Cu, Zn, Sn, Ti, Na, Sr, B, where aluminum melts or aluminumalloy melts should be mentioned in particular.

The fiber reinforcement including the porous matrix leads to aconsiderable increase in strength and damage tolerance compared with themonolithic ceramic to be found in the prior art. This leads to aquasi-ductile material behavior, so that brittle fracture is preventedand impacts or similar mechanical stresses must be classed asnon-critical. For example, collisions during movement of the meteringdevice that might be caused by faulty teaching of a robot are lessproblematic.

Surprisingly, the porosity of the composite material during the intake,holding and metering process of the melt, achieved by means of negativepressure, does not represent a technically relevant problem. Highmetering precision and exact quantity detection are possible.

This does not however rule out that an additional coating can beprovided.

In particular when the fibers and the matrix consist of the same oxide,such as Al₂O₃, this leads to prevention of corrosion in the material ofthe metering device and to a very favorable wetting ratio, for examplein melts of aluminum and its alloys. Additives of, for example,zirconium oxide can be advantageous here.

The invention is therefore also characterized in that the proportion byweight of the additive or matrix component zirconium oxide, wherenecessary reinforced with yttrium oxide, is 5% to 30%, in particular 12%to 25%, of the oxide ceramic of the matrix.

The favorable wetting behavior prevents for example the closure, such asa stopper, which can consist for example of SiC or of an oxide ceramicmaterial like that of the metering device, seizing up in the meteringdevice.

The wear is reduced. The cleaning effort due to hard-to-remove buildupsis reduced and damage is avoided.

As already mentioned, mass and structural changes basically do not occurwhen aggressive, for example alkaline aluminum melt alloys are handled,in particular when the matrix and the reinforcing fibers consist of orcontain aluminum oxide.

The wear is reduced and the service life is considerably prolonged.

Thanks to the lightweight construction resulting from the material,equipment and robotic systems are subjected to lower mechanical loading,permitting downsizing.

The movement duration of the metering device can be reduced incomparison to the prior art, and hence also the process durationoverall.

A further advantage of the lightweight construction is the thermal andtemperature insulation properties, such that by means of minortemperature falls, i.e. temperature drops in the melt, new possibilitiesfor processing are created. Energy savings are achievable.

The production technology ensures freedom in the geometrical design. Anycomplex geometries with undercuts can be achieved. The metering behaviorcan be improved by geometry changes or adjustments.

Due to the use in accordance with the invention of the oxide ceramicmaterials, larger-volume crucibles can be produced in comparison to theprior art. The low wall thickness enables the melt to be additionallytemperature-controlled by heating and cooling elements surrounding themetering device.

There is also the possibility that the stopper is designed hollow,allowing sensors such as temperature sensors to be integrated therein.

The opening, i.e. the spout, of the metering device can be designed suchthat melted droplets cannot stick.

It is furthermore possible to integrate strainer elements or filters toclean the melt.

The flow of the melt can be designed disturbance-free when flow aids areprovided inside the metering device whose negative form is replicated onthe die, onto which the fiber bundles are wound, or the flat fiberfabrics, mats and meshes are laid that were previously impregnated witha slurry containing oxide ceramic particles that form the matrix.

The invention is therefore also characterized by a method for producinga metering device, in particular a vacuum-assisted metering crucible orcontainer, for withdrawing and dispensing a melt, preferably a metalmelt, preferably a non-ferrous metal melt, in particular an aluminummelt or a melt containing aluminum, comprising the method steps

-   -   Impregnation of an arrangement of oxide ceramic fibers with a        slurry containing oxide ceramic particles,    -   Winding or laying of the impregnated arrangement of fibers onto        a die replicating the internal geometry of the metering device,    -   Drying of the arrangement laid or wound on the die.

The arrangement is then removed from the die, in particular fully orpartially removed from the mold. This is followed by sintering. Wherenecessary the metering device so produced is reworked.

One or more endless fiber bundles or flat structures, in particularfiber mats, fabrics or meshes, are used as the arrangement here.

In particular, it is provided that the drying process for forming agreen compact from the arrangement is performed in a temperature rangebetween 40° C. and 250° C., in particular between 80° C. and 150° C.

Drying and full or partial removal from the mold is followed bysintering, in particular at a temperature between 1000° C. and 1300° C.,preferably between 1150° C. and 1250° C.

Further details, advantages and features of the invention can begathered not only from the claims and in the features to be foundtherein, singly and/or in combination, but also from the followingdescription of preferred examples to be found in the drawing and fromtheir explanations.

The drawing shows in:

FIG. 1 an illustration of the principle of a metering device forwithdrawing and dispensing a melt with separately drawn stopper,

FIG. 2 a section from FIG. 1,

FIG. 3 a variant of the illustration in FIG. 2 and

FIG. 4 an illustration of the principle of a winding process.

The figures show purely by way of example a metering device forwithdrawing and dispensing a melt, in particular a metal melt, which isalso referred to as a metering crucible or container 10 and in thefollowing is called metering crucible for simplicity.

The metering crucible 10 has on the withdrawing/dispensing side a mouthopening 14 closable using a stopper 12 and merging into a conical andthen hollow-cylindrical section 16, 18.

The external diameter of the stopper 12, more precisely in its distalsection 20, matches the internal diameter of the spout or mouth opening14. The mouth opening can accordingly be closed or freed by axialmovement of the stopper 12.

The metering crucible 10 consists of a fiber-reinforced oxide ceramiccomposite material of the previously described material(s).

The porosity of the metering crucible 10 should be in the range of inparticular between 27% and 32%.

The stopper 12 can consist of an identical material to that of themetering crucible 10 or also for example of silicon carbide.

If the stopper 12 is produced from an oxide ceramic composite material,it can thus be designed hollow and for example contain one or moresensors to check the process and where necessary control or regulate it.

The metering crucible 10 is preferably produced by winding, althoughprepregs that can be laid onto a die replicating the internal geometryof the metering crucible 10, or a combination of these methods, can alsobe used.

Fiber bundles, so-called rovings, are wound onto the winding core, wherethe individual fiber filaments should have diameters between 5 μm and 20μm, in particular in the range between 10 μm and 12 μm. The densityshould be in the range between 2 g/cm³ and 6 g/cm³, preferably between2.5 g/cm³ and 3.2 g/cm³.

Before winding onto the winding core, the fiber bundles are passedthrough a slurry and thereby impregnated. The slurry contains theceramic particles forming the matrix of the composite body.

The proportion of ceramic particles can be 10% by volume to 50% byvolume, in particular 20% by volume to 40% by volume, relative to thetotal volume of the slurry.

In particular, a water-based slurry is used with preferably organicadditives, for example polyols, polyvinyl alcohols or polyvinylpyrrolidones, dispersion binders, preferably styrene acrylatedispersions.

The slurry can contain at least 10% by wt. to 20% by wt., preferably atleast 24% by wt., e.g. 21-35% by wt., of glycerin relative to the totalweight of the ceramic particles.

Both for the ceramic particles and for the fibers, a material inparticular from the group Al₂O₃, SiO₂, ZrO₂, Y₂O₃, TiO₂, CaO, MgO,Y₂O₃-stabilized ZrO₂ is conceivable as the oxide ceramic.

If an aluminum melt or an aluminum alloy melt is to be metered using themetering crucible 10, Al₂O₃ should be used as the material both for thematrix, i.e. accordingly the ceramic particles, and for the fibers.

The slurry can contain if necessary additives such as ZrO₂, where theproportion can be between 5% and 30%, in particular between 12% and 25%as a % by weight of the entire powder quantity of the ceramic metaloxide.

The proportion by volume of the ceramic particles should be 20 to 50% byvolume relative to the total volume of the slurry.

The corresponding impregnated fiber bundles are now wound onto thewinding core, then dried, in particular in the temperature range between40° C. and 250° C., preferably in the range between 80° C. and 150° C. Abody thus produced is divided and removed from the winding core. This isfollowed by sintering in the temperature range between 1000° C. and1300° C., in particular between 1150° C. and 1250° C. If necessaryreworking takes place and then use of the metering crucible 10 thusproduced.

The drying duration is temperature-dependent and is between 2 h and 48h, preferably between 12 h and 24 h.

Sintering is done over a temperature/time curve with various holdingstages and durations, where the holding duration at the maximumtemperature should be between 5 min and 24 h, preferably between 1 h and12 h.

Due to the winding technique used, the geometry of the metering crucible10 can be varied to the required extent depending on the geometry of thewinding core. This is illustrated in principle in FIGS. 2 and 3. Thereis thus the possibility of varying the opening angle of the conicalsection 16 to the required extent. In FIG. 2 the angle α1 is smallerthan the angle α2 in FIG. 3. Furthermore, the length of the spout 14 canbe varied, as is made clear by a comparison of FIGS. 2 and 3 in respectof the sections S1, S2. The length of the conical section 16 can also bevaried (L1<L2).

There is furthermore the possibility of varying the wall thickness ofthe component or of designing the end sections of the winding core suchthat flow aids are created inside the cones, as indicated purely inprinciple by FIG. 3.

For example ribs can be formed, preferably in helical form. Wavestructures can also be provided running concentrically about thelongitudinal axis of the metering crucible, to affect to the requiredextent the flow behavior of the melt.

In particular it is provided that the fiber volume content of themetering device is 35% to 50%, preferably 32% to 42%.

The following must be set forth regarding the winding technique.

Winding processes are used to produce rotation-symmetrical parts. Theinternal geometry of the object is predetermined by the so-calledwinding core on which the fibers impregnated with the matrix are laid.

For the winding core, a distinction is made between reusable, lost,meltable and strippable cores. In the present case, the meteringcrucibles are removed from the core, such that the latter can be usedagain. For smaller components, meltable cores are frequently used, andstrippable cores for components of larger diameter.

Winding is usually performed with a winding machine matching a CNClathe. The winding core is here clamped at one of its ends in athree-jaw chuck and at the other end mounted for example on a tailstock.

To wind rovings, i.e. fiber bundles, which can for example comprise 100or more individual fibers, so-called filaments, onto the winding core,they are unwound from a spool receptacle. Then the rovings can passdeflecting pulleys, by means of which the tension of the rovings is set.The fiber bundle is now passed through a thread eye over furtherdeflecting pulleys and through a slurry bath of which the compositionhas been described above. After impregnation of the fibers, they arepassed over one or more further deflecting pulleys, which likewisedetermine the thread tension and, by the number of revolutions, thewinding speed and the length of the consumed fiber strand, centered by athread eye, and laid on the winding core as it rotates. The threadtension also has a greater significance here. If it is too low, thefibers are not pressed onto the winding core to a sufficient extent. Ifthe tension is too high, the slurry cannot penetrate sufficientlybetween the individual fiber filaments, and tearing of the roving mightensue.

After the winding process, the wound fiber architecture is bonded usingpeel ply. This is intended to provide an even surface, compact it bydisplacing excess slurry and hence increase the fiber volume content,while additionally protecting the component.

In circumferential winding, also called radial winding, the rovings arelaid parallel, as can be seen in the illustration in FIG. 4. Withcross-winding, the rovings are laid from one end to the other end, inorder to provide a fiber reinforcement in the x and y directions too.The winding angle is measured from the laid fiber strand, against therotation axis, and influences the absorption of axial loads.

If a wound part has purely unidirectional circumferential windings, i.e.if the angle α is around 90°, very high tensile strengths are achievablein the tangential orientation. If the winding angle is <45°, higheraxial loads are absorbed. With reinforcement in the axial direction,i.e. with small winding angles, the problem arises during productionthat fixing of the roving at the end of the body is no longer possible.

Various computation programs are available for coordination of thewinding type, winding angle and number of layers (fiber requirement).

After the winding process, the wound fiber architecture is bonded usinga peel ply to obtain an even surface. Compaction is also achieved bydisplacing excess slurry, increasing the fiber volume content while thecomponent is additionally protected. This is followed by drying and thesintering process.

The following represents an example:

Firstly, oxide ceramic prepregs are produced. To do so, fabric made fromaluminum oxide fibers (>99% Al₂O₃) is impregnated with a water-basedslurry containing oxide ceramic particles. The filament diameter is10-12 μm and the yarn fineness is 20,000 denier. The slurry has a solidscontent of 30% by volume, consisting of 80% by wt. Al₂O₃ particles and20% by wt. ZrO₂ particles. The mean particle size is 1 μm. As adispersant, 2% by weight of polyacrylic acid is added. After a reductionin the water content of the infiltrated fiber architecture, theresultant prepreg can be processed by cutting it to size and laying itonto a die replicating the internal contour of the metering crucible.After that, the die loaded with the prepreg is clamped into a windingdevice. Then the aluminum oxide fiber rovings (>99% Al₂O₃) of 20,000denier yarn fineness are passed from a spool receptacle over deflectingpulleys and through an immersion bath, and laid on the rotating windingcore. The rovings are centered by a thread eye. The thread tension is inthe range from 10 to 90 N and is set using the deflecting pulleys. Theslurry inside the immersion bath has a solids content of 32% by volumeof ceramic particles relative to the total volume of the slurry,consisting of 80% Al₂O₃ particles and 20% ZrO₂ particles. The meanparticle size is 1 μm. As a dispersant, 2% by weight of polyacrylic acidis added. The wound fiber architecture of the shaped composite materialis consolidated by reducing the water content, so that a green compactis obtained. After drying, the wound fiber architecture can be removedfrom the core. This is followed by sintering at 1200° C. Reworking canbe performed by turning, milling or grinding.

1-29. (canceled)
 30. A metering device (10), preferably a meteringcrucible or container for vacuum-assisted metering, for withdrawing anddispensing a melt, preferably a metal melt, in particular a non-ferrousmetal melt, in particular an aluminum melt or a melt containingaluminum, the metering device (10) comprising an oxide-fiber-reinforcedoxide ceramic composite material.
 31. The metering device according toclaim 30, wherein the metering device (10) is coated on the insideand/or on the outside with at least one preferably closed-pore coatingor compacted.
 32. The metering device according to claim 30, wherein oneor more coatings of a thickness d of 50 μm≤d≤2 mm are applied to theoxide-fiber-reinforced oxide ceramic composite material as the basicbody of the metering device (10), in particular the coating has adensity of at least 95%, preferably at least 97% of the theoreticaldensity of the material of which the coating consists.
 33. The meteringdevice according to claim 30, wherein the composite material containsoxide ceramic fibers, formed from preferably at least one material fromthe group Al₂O₃, SiO₂, ZrO₂, Y₂O₃, TiO₂, CaO, MgO, Y₂O₃-stabilized ZrO₂,and/or the composite material contains an oxide ceramic matrix, formedfrom preferably at least one material from the group Al₂O₃, SiO₂, ZrO₂,Y₂O₃, TiO₂, CaO, MgO, Y₂O₃-stabilized ZrO₂.
 34. The metering deviceaccording to claim 33, wherein the matrix and the fibers consist of orcontain the same oxide ceramic material(s), or the main constituents ofthe oxide ceramic materials match, in particular the matrix and thefibers consist of or contain Al₂O₃ as the main constituent.
 35. Themetering device according to claim 30, wherein the metal in thecomposite material and that of the melt or main constituent of the meltis identical.
 36. The metering device according to claim 30, wherein theopen porosity of the metering device (10) or of theoxide-fiber-reinforced oxide ceramic composite material is between 20%and 40%, in particular between 27% and 32%.
 37. The metering deviceaccording to claim 30, wherein the density p of the fibers is 2g/cm³<ρ<6 g/cm³, in particular 3.0 g/cm³<ρ<4.0 g/cm³ and/or the fiberdiameter is 5 μm to 20 μm, in particular 10 μm to 12 μm.
 38. Themetering device according to claim 30, wherein the metering device (10)has a metallic structure which is provided on the melt side with aninherently rigid body consisting of the oxide ceramic composite materialand inserted into the metering device.
 39. The metering device accordingto claim 30, wherein the metering device (10) is produced by windingfibers onto a die replicating the internal geometry of the meteringdevice and/or by the use of textile mats, meshes and fabrics from theoxide ceramic fibers.
 40. The metering device according to claim 30,wherein the oxide ceramic fibers consist of endless fibers, inparticular in the form of endless fiber bundles, short fibers or acombination thereof.
 41. The metering device according to claim 30,wherein the metering device (10) has a wall thickness W_(D) of 1mm≤W_(D)≤20 mm, in particular 1 mm≤W_(D)≤3 mm, and/or the meteringdevice (10) has load-appropriate fiber reinforcements, in particular inthe withdrawing and dispensing area.
 42. The metering device accordingto claim 30, wherein flow aids are formed on the inside of the meteringdevice (10).
 43. The metering device according to claim 30, wherein themetering device (10) is closable by a stopper (12) consisting of orcontaining a material from the group SiC or the material of the matrix,in particular the stopper (12) is designed hollow, at least one sensorsuch as a temperature sensor being arranged preferably inside thestopper.
 44. A method for producing a metering device (10), such as ametering crucible or container for vacuum-assisted metering, forwithdrawing and dispensing a melt, preferably a metal melt, inparticular a non-ferrous metal melt, in particular an aluminum melt or amelt containing aluminum, comprising at least the method steps:impregnation of an arrangement of oxide ceramic fibers with a slurrycontaining oxide ceramic particles, winding or laying of the impregnatedarrangement of fibers onto a die replicating the internal geometry ofthe metering device (10), drying of the arrangement laid or wound ontothe die, removal of the arrangement and sintering thereof.
 45. Themethod according to claim 44, wherein the arrangement of the fibers isdried at a temperature between 40° C. and 250° C., in particular between80° C. and 150° C., and/or the arrangement of the fibers is sintered ata temperature between 1000° C. and 1300° C., in particular between 1150°C. and 1250° C.
 46. The method according to claim 44, wherein one ormore endless fiber bundles and/or flat fiber structures, in particularfiber mats, fabrics or meshes, are used as the arrangement.
 47. Themethod according to claim 44, wherein the sintered and where necessaryreworked arrangement for producing the metering device (10) is coated atleast in some areas, in particular at least on the outside, to form apreferably closed-pore coating, in particular glass solder ororganometallic compounds are used as the coating material.
 48. Themethod according to claim 44, wherein a ceramic coating, aprecursor-based coating or a glass-like coating is applied to the basicbody, in particular the coating is applied by thermal spraying.
 49. Ause of a metering device (10) according to claim 30 for withdrawing amelt, transporting the melt in the metering device (10) by moving andpouring the melt into a mold.